Fabricating method for multilayer printed circuit board

ABSTRACT

A fabrication method for a multilayer printed circuit board includes: forming a first circuit-forming pattern and a first insulation layer, into which the first circuit-forming pattern is inserted, on a first carrier; forming inner circuit patterns and inner insulation layers over the first insulation layer, and forming inner vias connecting the inner circuit patterns positioned on different insulation layers; forming a second circuit-forming pattern on a second carrier and inserting the second circuit-forming pattern into a second insulation layer on an outermost side; removing the first carrier and the second carrier; forming circuit-forming grooves by removing the first circuit-forming pattern and the second circuit-forming pattern, and forming via-forming indentations connected with the circuit-forming grooves; and forming outer circuit patterns and outer vias by filling the circuit-forming grooves and the via-forming indentations with a conductive material. This can provide a thin printed circuit board having high reliability and fine-lined circuits.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2007-0069275 filed with the Korean Intellectual Property Office onJul. 10, 2007, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a fabricating method for a multilayerprinted circuit board.

2. Description of the Related Art

With electronic devices being geared towards higher functionalities andsmaller sizes, the need is increasing for enhancing the functions ofcircuit components and increasing package density. There is also a needfor improving the module to which the circuit components are joined, forincreasing package density and functionality. The current trend is tomount the circuit components on a circuit board having a multilayerstructure, so that the package density may be improved. In particular,the multilayer printed circuit board that uses connection by inner viasis commonly utilized as a means for increasing circuit density.Furthermore, the component-integrated circuit board is being developed,in which wiring patterns connect the mounting area with the LSI areas orthe components by as short a distance as possible to reduce space.

With the printed circuit board continuously becoming lighter, thinner,and simpler, the width and pitch of the circuit patterns are reachingvalues lower than 50 μm and even 25 μm. In such conditions of minutevalues, however, the circuit patterns are subject to becoming detachedduring the processing procedures, which can lower production yield,while bending and warpage, etc., can occur in the board. There may alsobe other problems affecting reliability, such as problems in migrationresistance and heat resistance after moisture absorption, etc.

SUMMARY

An aspect of the invention is to provide a method of fabricating a thinmultilayer printed circuit board.

Another aspect of the invention is to provide a fabrication method for amultilayer printed circuit board, which enables fine-lined circuitswhile providing high reliability.

One aspect of the invention provides a method of fabricating amultilayer printed circuit board, which includes: forming a firstcircuit-forming pattern and a first insulation layer, into which thefirst circuit-forming pattern is inserted, on a first carrier; forminginner circuit patterns and inner insulation layers over the firstinsulation layer, and forming inner vias connecting the inner circuitpatterns positioned on different insulation layers; forming a secondcircuit-forming pattern on a second carrier and inserting the secondcircuit-forming pattern into a second insulation layer on an outermostside; removing the first carrier and the second carrier; formingcircuit-forming grooves by removing the first circuit-forming patternand the second circuit-forming pattern, and forming via-formingindentations connected with the circuit-forming grooves; and formingouter circuit patterns and outer vias by filling the circuit-forminggrooves and the via-forming indentations with a conductive material.

Another aspect of the invention provides a method of fabricating amultilayer printed circuit board, which includes: forming a firstcircuit-forming pattern and a first insulation layer, into which thefirst circuit-forming pattern is inserted, on a carrier; forming innercircuit patterns and inner insulation layers over the first insulationlayer, and forming inner vias connecting the inner circuit patternspositioned on different insulation layers; forming a secondcircuit-forming pattern on a second insulation layer on an outermostside, and inserting the second circuit-forming pattern into the secondinsulation layer; removing the carrier; forming circuit-forming groovesand via-forming indentations connected with the circuit-forming grooves,by removing the first circuit-forming pattern and the secondcircuit-forming pattern; and forming outer circuit patterns and outervias by filling the circuit-forming grooves and the via-formingindentations with a conductive material.

The method of fabricating a multilayer printed circuit board accordingto certain embodiments of the invention may include one or more of thefollowing features. For example, at least one of the firstcircuit-forming pattern and the second circuit-forming pattern can beformed from a dissolvable material, such as a water-soluble resin. Thefirst circuit-forming pattern and/or the second circuit-forming patterncan also be formed from a detachable photosensitive resist.

At least one of the first carrier and the second carrier can be formedfrom any one of a tape, a film, and a sheet, and can be removed bydetaching. Also, the first circuit-forming pattern and/or the secondcircuit-forming pattern can be formed from a metal foil, and can beremoved by etching. The carrier can be any one of a tape, a film, and asheet, and can be removed by detaching, or can be made from a metalfoil, and can be removed by etching.

The conductive material filled in the circuit-forming grooves and thevia-forming indentations may be filled in by plating. The method offabricating a multilayer printed circuit board can further includeremoving a portion of the conductive material by a leveling process,after the conductive material is filled in. Also, after the levelingprocess, a solder resist can be formed on at least one of the firstinsulation layer and the second insulation layer, and openings can beformed such that the outer circuit patterns are revealed.

The inner circuit patterns can be formed by pressinginner-circuit-forming patterns formed on the inner insulation layers,such that the inner-circuit-forming patterns are inserted into the innerinsulation layers, and then removing the inner-circuit-forming patterns;and filling a conductive material in circuit-forming grooves formed byremoving the inner-circuit-forming patterns. The inner vias can beformed by processing via-forming indentations connected with the innercircuit patterns in the circuit-forming grooves, and then filling aconductive material in the via-forming indentations.

Forming the first circuit-forming pattern on the first carrier mayinclude detachably securing a pair of the first carriers to each otherand forming the first circuit-forming pattern on each of the firstcarriers. Forming the first circuit-forming pattern on the carrier mayinclude detachably securing a pair of the carriers to each other andforming the first circuit-forming pattern on each of the carriers.

Yet another aspect of the invention provides a method of fabricating amultilayer printed circuit board, which includes: forming a firstcircuit-forming pattern and a via-forming pattern on a first carrier,and forming a first insulation layer; repeatedly forming inner circuitpatterns and inner insulation layers over the first insulation layer byprocesses of forming circuit-forming patterns and imprinting, andforming inner vias connecting the inner circuit patterns positioned ondifferent insulation layers; forming a second circuit-forming pattern ona second carrier and inserting the first circuit-forming pattern and thesecond circuit-forming pattern respectively into the first insulationlayer and a second insulation layer on an outermost side; removing thefirst carrier and the second carrier; forming circuit-forming grooves byremoving the first circuit-forming pattern and the secondcircuit-forming pattern, and forming via-forming indentations connectedwith the circuit-forming grooves; and forming outer circuit patterns andouter vias by filling the circuit-forming grooves and the via-formingindentations with a conductive material.

Additional aspects and advantages of the present invention will be setforth in part in the description which follows, and in part will beobvious from the description, or may be learned by practice of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a method of fabricating a multilayerprinted circuit board according to an embodiment of the invention.

FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6A, FIG. 6B, FIG. 7, FIG. 8, FIG.9, FIG. 10, FIG. 11, and FIG. 12 are cross-sectional views representinga method of fabricating a multilayer printed circuit board according toan embodiment of the invention.

FIG. 13 is a flowchart illustrating a method of fabricating a multilayerprinted circuit board according to another embodiment of the invention.

FIG. 14, FIG. 15, FIG. 16, FIG. 17, and FIG. 18 are cross-sectionalviews representing a method of fabricating a multilayer printed circuitboard according to another embodiment of the invention.

FIG. 19 is a flowchart illustrating a method of fabricating a multilayerprinted circuit board according to still another embodiment of theinvention.

FIG. 20, FIG. 21, FIG. 22, FIG. 23, FIG. 24, and FIG. 25 arecross-sectional views representing a method of fabricating a multilayerprinted circuit board according to still another embodiment of theinvention.

FIG. 26 is a flowchart illustrating a method of fabricating a multilayerprinted circuit board according to yet another embodiment of theinvention.

FIG. 27 and FIG. 28 are cross-sectional views representing a method offabricating a multilayer printed circuit board according to yet anotherembodiment of the invention.

DETAILED DESCRIPTION

As the invention allows for various changes and numerous embodiments,particular embodiments will be illustrated in drawings and described indetail in the written description. However, this is not intended tolimit the present invention to particular modes of practice, and it isto be appreciated that all changes, equivalents, and substitutes that donot depart from the spirit and technical scope of the present inventionare encompassed in the present invention. In the description of thepresent invention, certain detailed explanations of related art areomitted when it is deemed that they may unnecessarily obscure theessence of the invention.

FIG. 1 is a flowchart illustrating a method of fabricating a multilayerprinted circuit board according to an embodiment of the invention.

Referring to FIG. 1, a method of fabricating a multilayer printedcircuit board according to an embodiment of the invention can includeforming a first circuit-forming pattern and a first insulation layer,into which the first circuit-forming pattern is inserted, on a firstcarrier; forming inner circuit patterns and inner insulation layers overthe first insulation layer by way of build-up processes, and forminginner vias that connect inner circuit patterns positioned on differentinner insulation layers; forming a second circuit-forming pattern on asecond carrier and iinserting the second circuit-forming pattern into asecond insulation layer on an outermost side; removing the first carrierand the second carrier; forming circuit-forming grooves by removing thefirst circuit-forming pattern and the second circuit-forming pattern,and forming via-forming indentations connected with the circuit-forminggrooves; and forming outer circuit patterns and outer vias by fillingthe circuit-forming grooves and the via-forming indentations with aconductive material.

In the method of fabricating a multilayer printed circuit boardaccording to this embodiment, the first and second circuit-formingpatterns may be formed respectively on the first and second carriers,inserted into insulation layers and then removed, after which aconductive material may be filled in the resultant circuit-forminggrooves to form the outer circuit patterns. This will make it possiblenot only to fabricate a thin printed circuit board but also to increasethe reliability of the board. Also, since the first and second carrierscan be formed not only from metal but also from other materials such astape, film, and sheets, the fabrication costs may be reduced.

An example of a method of fabricating a multilayer printed circuit boardaccording to an embodiment of the invention will now be described withreference to FIG. 2 through FIG. 12.

FIG. 2 is a cross-sectional view illustrating a first circuit-formingpattern 122 formed on a first carrier 120, in a method of fabricating amultilayer printed circuit board according to an embodiment of theinvention.

The first carrier 120 can be made not only of a metal foil, but also ofvarious other materials such as a tape, film, or sheet. The firstcarrier 120 may be removed in a subsequent process (see FIG. 8), wherethe method of removal may vary in accordance to the material of thefirst carrier 120. That is, if the first carrier 120 is formed from ametal foil, the first carrier 120 may be removed by etching, and if thefirst carrier 120 is formed from a tape, film, or sheet, the firstcarrier 120 may be peeled off.

The first circuit-forming pattern 122 formed on the first carrier 120can be formed from a dissolvable material. For example, the firstcircuit-forming pattern 122 may be formed from a water-soluble resin,etc., such as modified alkyd resin, phenol resin, melamine-modifiedacrylic resin, and amino resin, etc. The first circuit-forming pattern122 may also be formed from a peelable photosensitive resist.

Afterwards, the first circuit-forming pattern 122 can be dissolved ordetached in a subsequent process (see FIG. 9) to form circuit-forminggrooves, which can be used to form an outer circuit pattern. The methodof forming the first circuit-forming pattern 122 on the first carrier120 may be substantially the same as the general method of forming acircuit pattern on a printed circuit board, and thus will not bepresented in further detail.

FIG. 3 is a cross-sectional view illustrating a first insulation layer142 formed over the first circuit-forming pattern 122 illustrated inFIG. 2.

As illustrated in FIG. 3, the first insulation layer 142 can be formedon the first carrier 120 with the first circuit-forming pattern 122inserted therein. The first insulation layer 142 may serve to insulatethe layers of inner circuit patterns and outer circuit patterns, whichwill be formed later. An outer circuit pattern 220, formed in thegrooves remaining when the first circuit-forming pattern 122 is removed,may be inserted inside the first insulation layer 142.

The first insulation layer 142 can be formed from a thermosetting resin.Examples of thermosetting resins include phenol resins, melanin resins,urea resins, urea resins, epoxy resins, phenoxy resins, epoxy modifiedpolyimide resins, unsaturated polyester resins, polyimide resins,urethane resins, diallyl phthalate resins, etc. Such thermosettingresins can be used alone or in a mixed resin of two or more types.

A hardening agent can be used in the thermosetting resin, examples ofwhich include polyphenol-based hardening agents, polyamine-basedhardening agents, carboxylic acid hydrazide types, dicyan diamide, nylonsalts and phosphates of imidazole type polyamine, Lewis acids and theiramine chelates, etc. Such hardening agents can be used alone or in amixture of two or more agents.

The first insulation layer 142 can be formed from a thermoplastic resin.Examples of thermosetting resins include polyether sulfone, polysulfone,polyether imide, polystyrene, polyethylene, polyallylate,polyamide-imide, polyphenylene sulfide, polyether ketone, polyoxybenzoate, polyvinyl chloride, polyvinyl acetate, polyacetal,polycarbonate, etc. Such thermoplastic resins can be used alone, or twoor more resins can be used together.

FIG. 4 and FIG. 5 are cross-sectional views illustrating inner circuitpatterns 160 formed over the first insulation layer 142, in a multilayerprinted circuit board according to an embodiment of the invention.

Referring to FIGS. 4 and 5, inner circuit patterns 160 and inner vias162 may be formed over the first insulation layer 142 by build-upprocesses. That is, inner circuit patterns 160 can be formed bysemi-additive or subtractive processes, etc., and inner vias 162 can beformed by laser processing, etc. The inner circuit patterns 160positioned on different layers can be insulated by the inner insulationlayers 144. The number of layers to which the inner insulation layers144 are stacked may vary according to design conditions, etc. Over theinner circuit patterns of the outermost layer, a second insulation layer146 may be formed (see FIG. 6 a or FIG. 6 b).

FIG. 6 a is a cross-sectional view illustrating a second circuit-formingpattern 126 formed on the second insulation layer 146, in a method offabricating a multilayer printed circuit board according to anembodiment of the invention.

Referring to FIG. 6 a, the second circuit-forming pattern 126 can beformed on the second insulation layer 146 by a typical method forforming circuit patterns. The second circuit-forming pattern 126 maylater be inserted into the second insulation layer 146 and then removed,to provide circuit-forming grooves for forming outer circuit patterns220. The method of forming the second circuit-forming pattern 126, etc.,may be substantially the same as the method for forming the firstcircuit-forming pattern 122, and thus will not be presented in furtherdetail.

FIG. 6 b is a cross-sectional view illustrating a second circuit-formingpattern 126 formed on the second insulation layer 146, in a method offabricating a multilayer printed circuit board according to anotherembodiment of the invention.

Referring to FIG. 6 b, the second circuit-forming pattern 126 can beformed on a second carrier 124 by a typical method for forming circuitpatterns. The compositions and fabricating methods for the secondcarrier 124 and the second circuit-forming pattern 126 may besubstantially the same as those for the first carrier 120 and the firstcircuit-forming pattern 122. By pressing the second carrier 124 from theoutside, the second circuit-forming pattern 126 formed on the secondcarrier 124 can be inserted into the second insulation layer 146.

FIG. 7 is a cross-sectional view illustrating the first circuit-formingpattern 122 and second circuit-forming pattern 126 inserted into thefirst insulation layer 142 and second insulation layer 146 respectively,in a method of fabricating a multilayer printed circuit board accordingto an embodiment of the invention.

Referring to FIG. 7, the first carrier 120 and the second carrier 124,positioned on either side in FIG. 6 a and FIG. 6 b, may be pressedtogether such that the first circuit-forming pattern 122 and secondcircuit-forming pattern 126 are inserted inside the first insulationlayer 142 and second insulation layer 146, respectively. When pressingthe first and second carriers 120, 124, heat can be applied, in somecases, according to the properties of the first and second insulationlayers 142, 146.

FIG. 8 is a cross-sectional view illustrating the removal of the firstcarrier 120 and the second carrier 124, in a method of fabricating amultilayer printed circuit board according to an embodiment of theinvention.

Referring to FIG. 8, the first carrier 120 and second carrier 124positioned on the first insulation layer 142 and second insulation layer146 can be removed by detaching or etching. That is, if the firstcarrier 120 and/or second carrier 124 is made from a metal foil, etc.,the first carrier 120 and/or second carrier 124 can be removed byetching, and if the first carrier 120 and/or second carrier 124 is madefrom a film, sheet, or tape, etc., the first carrier 120 and/or secondcarrier 124 can be peeled off. By removing the first and second carriers120, 124, the first circuit-forming pattern 122 and the secondcircuit-forming pattern 126 may be exposed to the exterior.

FIG. 9 is a cross-sectional view illustrating circuit-forming grooves180 and via-forming indentations 182 formed after removing the firstcircuit-forming pattern 122 and second circuit-forming pattern 126, in amethod of fabricating a multilayer printed circuit board according to anembodiment of the invention.

Referring to FIG. 9, the first circuit-forming pattern 122 and secondcircuit-forming pattern 126 may be removed, as described above, bydissolving or peeling, etc. As a result of removing the first and secondcircuit-forming patterns 122, 126, circuit-forming grooves 180 may beformed. In addition, via-forming indentations 182 may be formed whichconnect to the circuit-forming grooves 180, with the via-formingindentations 182 connecting also to the inner circuit patterns 160. Thevia-forming indentations 182 can be formed by laser processing, etc.

FIG. 10 is a cross-sectional view illustrating the circuit-forminggrooves 180 and the via-forming indentations 182 filled in with aconductive material by performing plating, in a method of fabricating amultilayer printed circuit board according to an embodiment of theinvention.

Referring to FIG. 10, the circuit-forming grooves 180 and via-formingindentations 182 can be filled in by plating with a conductive materialsuch as copper, gold, tin, zinc, etc. The plating may be performed onjust one side, or may be performed on both sides as is the case in FIG.10. By filling in the conductive material, outer circuit patterns 220and outer vias 222 may be formed. Interlayer connection can be providedbetween the inner circuit patterns 160 and outer circuit patterns 220 bythe outer vias 222.

Besides performing plating, the circuit-forming grooves 180 andvia-forming indentations 182 can also be filled in with conductivematerials by printing metal ink, or by filling with conductive paste, toform the outer circuit patterns 220 and outer vias 222.

FIG. 11 is a cross-sectional view illustrating the plated board afterapplying a surface processing, in a method of fabricating a multilayerprinted circuit board according to an embodiment of the invention.

Referring to FIG. 11, the surfaces of the layers formed by plating canbe processed by methods such as mechanical polishing and etching, etc.As a result of the surface processing, the outer circuit patterns 220,and the first and second insulation layers 142, 146 may be exposed tothe exterior.

FIG. 12 is a cross-sectional view illustrating solder resists 240 formedover the first insulation layer 142 and second insulation layer 146, ina method of fabricating a multilayer printed circuit board according toan embodiment of the invention.

Referring to FIG. 12, the solder resists 240 may be formed over thefirst and second insulation layers. 142, 146. Openings 242 may be formedin the solder resists 240, through which the outer circuit patterns 220can be exposed to the exterior. With the openings 242 formed in theboard, a semiconductor chip (not shown), etc., can be mounted onto theboard in a subsequent process.

FIG. 13 is a flowchart illustrating a method of fabricating a multilayerprinted circuit board according to another embodiment of the invention.

Referring to FIG. 13, a method of fabricating a multilayer printedcircuit board according to another embodiment of the invention caninclude forming a first circuit-forming pattern and a first insulationlayer, into which the first circuit-forming pattern is inserted, on afirst carrier; repeatedly forming inner circuit patterns and innerinsulation layers over the first insulation layer, by repeating thoseprocesses in which inner-circuit-forming patterns are formed, insertedinto the inner insulation layers, and then removed, and forming innervias that connect inner circuit patterns positioned on different innerinsulation layers; forming a second circuit-forming pattern on a secondcarrier and inserting the second circuit-forming pattern into the secondinsulation layer on an outermost side; removing the first carrier andthe second carrier; forming circuit-forming grooves by removing thefirst circuit-forming pattern and the second circuit-forming pattern,and forming via-forming indentations connected with the circuit-forminggrooves; and forming outer circuit patterns and outer vias by fillingthe circuit-forming grooves and the via-forming indentations with aconductive material.

In the method of fabricating a multilayer printed circuit boardaccording to this embodiment, almost all of the operations besides themethod of forming the inner circuit patterns may be substantially thesame as or may be in correspondence with the operations illustrated inFIG. 1. Therefore, the following descriptions will deal only with themethod of forming the inner circuit patterns, with reference to FIGS. 14to 18.

FIG. 14 is a cross-sectional view illustrating an inner-circuit-formingpattern 260 formed on a first insulation layer 142, in a method offabricating a multilayer printed circuit board according to anotherembodiment of the invention.

Referring to FIG. 14, the inner-circuit-forming pattern 260 can beformed from a dissolvable water-soluble resin or a detachablephotosensitive resin, etc. The method of forming theinner-circuit-forming pattern 260 is substantially the same as that forthe first circuit-forming pattern 122 positioned on the first carrier120, and thus will not be presented in further detail.

FIG. 15 is a cross-sectional view illustrating the inner-circuit-formingpattern 260 pressed and inserted into the first insulation layer 142, ina method of fabricating a multilayer printed circuit board according toanother embodiment of the invention.

Referring to FIG. 15, the inner-circuit-forming pattern 260 can bepressed by a plate (not shown), etc., to be inserted into the firstinsulation layer 142. As described above, the method of inserting theinner-circuit-forming patterns 260 into the first insulation layer 142may be substantially the same as the method for inserting the secondcircuit-forming pattern 126 into the second insulation layer 146.

FIG. 16 is a cross-sectional view illustrating the arrangement after theinner-circuit-forming pattern 260 has been removed, in a method offabricating a multilayer printed circuit board according to anotherembodiment of the invention.

Referring to FIG. 16, the inner-circuit-forming pattern 262 may beremoved by peeling or dissolving, to provide circuit-forming grooves180. As described above, if the inner-circuit-forming pattern 260 isformed from a water-soluble resin, etc., it can be removed bydissolving, and if it is formed from a detachable photosensitive resin,etc., it can be removed by peeling. Once the inner-circuit-formingpattern 260 is removed, the circuit-forming grooves 180 may be formed,by the use of which inner circuit patterns 160 can be formed.

FIG. 17 is a cross-sectional view illustrating via-forming indentations182 processed in, after removing the inner-circuit-forming pattern 260,in a method of fabricating a multilayer printed circuit board accordingto another embodiment of the invention.

Referring to FIG. 17, the via-forming indentations 182 can be formed bylaser processing, etc., which connect with the first circuit-formingpattern 122 formed on the first carrier 120. A conductive material suchas copper, etc., can be filled in the via-forming indentations 182,which allow interlayer connection between the inner circuit patterns 160and the first circuit-forming pattern 122.

FIG. 18 is a cross-sectional view illustrating an inner circuit pattern160 and inner vias 162 formed, in a method of fabricating a multilayerprinted circuit board according to another embodiment of the invention.

Referring to FIG. 18, a conductive material can be filled by platinginto the circuit-forming grooves 180 and via-forming indentations 182formed after removing the inner-circuit-forming pattern 260. Theconductive material can be filled in using a general plating process, orcan be filled in by printing conductive ink. The conductive material canalso be filled in using conductive paste.

In this way, a surface processing can be performed after filling in theconductive material, to expose the inner circuit pattern 160 to theexterior. Afterwards, these processes may be repeated to form innercircuit patterns 160 positioned on more layers, and then the processesillustrated in FIG. 6 a or FIG. 6 b through FIG. 12 can be performed tocomplete a multilayer printed circuit board.

FIG. 19 is a flowchart illustrating a method of fabricating a multilayerprinted circuit board according to still another embodiment of theinvention.

Referring to FIG. 19, a method of fabricating a multilayer printedcircuit board according to still another embodiment of the invention caninclude forming a first circuit-forming pattern and a via-formingpattern on a first carrier, and then forming a first insulation layer;repeatedly forming inner circuit patterns and inner insulation layersover the first insulation layer, by processes of forming circuit-formingpatterns and imprinting, and forming inner vias that connect innercircuit patterns positioned on different inner insulation layers;forming a second circuit-forming pattern on a second carrier andinserting the first circuit-forming pattern and the secondcircuit-forming pattern respectively into the first insulation layer andthe second insulation layer on the outermost sides; removing the firstcarrier and the second carrier; forming circuit-forming grooves byremoving the first circuit-forming pattern and the secondcircuit-forming pattern, and forming via-forming indentations connectedwith the circuit-forming grooves; and forming outer circuit patterns andouter vias by filling the circuit-forming grooves and the via-formingindentations with a conductive material.

In the method of fabricating a multilayer printed circuit boardillustrated in FIG. 19, the vias that connect the outer circuit patterns220 with the inner circuit patterns 160 may be formed by imprinting andremoving the via-forming pattern 128, and then filling in a conductivematerial into the removed portions.

An example of a method of fabricating a multilayer printed circuit boardaccording to still another embodiment of the invention will now bedescribed with reference to FIG. 20 through FIG. 25.

FIG. 20 is a cross-sectional view illustrating a first circuit-formingpattern 122 and a via-forming pattern 128 formed in order over a firstcarrier 120, in a method of fabricating a multilayer printed circuitboard according to still another embodiment of the invention.

Referring to FIG. 20, the via-forming pattern 128 may be formed by asubstantially same method as that used for the first circuit-formingpattern 122. The via-forming pattern 128 can be made with a relativelysmaller size than that of the first circuit-forming pattern 122. Thevia-forming pattern 128 may be removed in a subsequent process by amethod of dissolving or detaching, similar to the method of removing thefirst circuit-forming pattern 122.

FIG. 21 is a cross-sectional view illustrating a first insulation layer142 formed over the first carrier 120, in a method of fabricating amultilayer printed circuit board according to still another embodimentof the invention.

Referring to FIG. 21, the first circuit-forming pattern 122 and thevia-forming pattern 128 can be inserted and positioned within the firstinsulation layer 142. The thickness of the first insulation layer 142can be formed to be somewhat greater than the height of the via-formingpattern 128.

FIG. 22 is a cross-sectional view illustrating an inner-circuit-formingpattern 260 formed on the first insulation layer 142 to form an innercircuit pattern, in a method of fabricating a multilayer printed circuitboard according to still another embodiment of the invention.

Referring to FIG. 22, the inner-circuit-forming pattern 260 may beformed on the first insulation layer 142. The method of forming theinner-circuit-forming pattern 260 is as described with reference to FIG.14. The inner-circuit-forming pattern 260 may be connected with thevia-forming pattern 128 in a subsequent process.

FIG. 23 is a cross-sectional view illustrating the inner-circuit-formingpattern 260 pressed and inserted into the first insulation layer 142, ina method of fabricating a multilayer printed circuit board according tostill another embodiment of the invention.

Referring to FIG. 23, the inner-circuit-forming pattern 260 may bepressed and inserted inside the first insulation layer 142. Here,portions of the first circuit-forming pattern 122 may be placed incontact with the via-forming pattern 128.

FIG. 24 is a cross-sectional view after the inner-circuit-formingpattern 260 and the via-forming pattern 128, in a method of fabricatinga multilayer printed circuit board according to still another embodimentof the invention.

Referring to FIG. 24, the inner-circuit-forming pattern 260 andvia-forming pattern 128 may be removed by dissolving or peeling, etc.,to form circuit-forming grooves 180 and via-forming indentations 182.Through the circuit-forming grooves 180 and via-forming indentations182, the first circuit-forming pattern 122 formed on the first carrier120 may be exposed to the exterior. As resin, etc., may remain on theexposed first circuit-forming pattern 122, a plasma or chemicaldesmearing process may be performed to treat the first circuit-formingpattern 122 for resin residue, etc.

FIG. 25 is a cross-sectional view illustrating the circuit-forminggrooves 180 and via-forming indentations 182 filled with conductivematerial, in a method of fabricating a multilayer printed circuit boardaccording to still another embodiment of the invention.

Referring to FIG. 25, the circuit-forming grooves 180 and thevia-forming indentations 182 can be filled with conductive material by aprocess of plating, etc. As a result, an inner circuit pattern 160 andinner vias 162 may be formed. Then, the first circuit-forming pattern122 touching the outer vias 222 may be removed in a subsequent process,and conductive material can be filled into the resulting grooves to forman outer circuit pattern 220 that connects with the outer vias 222.

Although this particular embodiment is described to have the innercircuit patterns formed by forming, imprinting, and removing theinner-circuit-forming patterns 260, and then filling with conductivematerial, the embodiment is not thus limited, and it is apparent thatthe inner circuit patterns can be formed by build-up processes asillustrated in FIGS. 3 to 4.

FIG. 26 is a flowchart illustrating a method of fabricating a multilayerprinted circuit board according to yet another embodiment of theinvention.

Referring to FIG. 26, a method of fabricating a multilayer printedcircuit board according to yet another embodiment of the invention caninclude forming a first circuit-forming pattern on each of firstcarriers that are attached to each other, and then forming a firstinsulation layer; repeatedly forming inner circuit patterns and innerinsulation layers over the first insulation layers by way of build-upprocesses, and forming vias that connect inner circuit patternspositioned on different inner insulation layers; forming secondcircuit-forming patterns on second carriers and inserting the firstcircuit-forming patterns and the second circuit-forming patterns intothe first insulation layers and the second insulation layers on theoutermost sides; separating the pair of first carriers and removing thefirst carriers and the second carriers; forming circuit-forming groovesby removing the first circuit-forming patterns and-the secondcircuit-forming patterns, and forming via-forming indentations connectedwith the circuit-forming grooves; and forming outer circuit patterns andouter vias by filling the circuit-forming grooves and the via-formingindentations with conductive material.

In the method of fabricating a multilayer printed circuit boardaccording to this embodiment, a pair of first carriers 120 may beattached to each other, as illustrated in FIG. 27, after which theprocesses illustrated in FIG. 2 through FIG. 7 may be performed for eachfirst carrier 120. As the processes illustrated in FIGS. 8 to 12 may beperformed after separating the adjoined first carriers 120, the processtimes may be reduced.

FIG. 27 is a cross-sectional view illustrating a pair of first carriers120 attached to each other, in a method of fabricating a multilayerprinted circuit board according to yet another embodiment of theinvention.

Referring to FIG. 27, the first carriers 120 may be joined by anadhesive film 300 such that they are detachable, so that they may beseparated in a subsequent process. Each of the first carriers 120 mayhave a first circuit-forming pattern 122 formed thereon.

FIG. 28 is a cross-sectional view illustrating inner circuit patterns160 and inner vias 162 formed over the pair of first carriers 120 bybuild-up processes or imprinting processes, in a method of fabricating amultilayer printed circuit board according to yet another embodiment ofthe invention.

Referring to FIG. 28, it can be observed that identical circuit layersmay be formed on either side of the adhesive film 300. The method offorming the circuit layers may be substantially the same as the methoddescribed with reference to FIG. 2 through FIG. 7. Then, afterseparating the circuit layers by removing the adhesive film 300, theprocesses illustrated in FIGS. 8 to 12 can be performed to fabricate themultilayer printed circuit board.

As set forth above, certain aspects of the invention provide afabrication method for a thin multilayer printed circuit board.

Certain aspects of the invention also provide a fabrication method for amultilayer printed circuit board, which enables the forming offine-lined circuits and provides high reliability.

While the spirit of the invention has been described in detail withreference to particular embodiments, the embodiments are forillustrative purposes only and do not limit the invention. It is to beappreciated that those skilled in the art can change or modify theembodiments without departing from the scope and spirit of theinvention.

1. A method of fabricating a multilayer printed circuit board, themethod comprising: forming a first circuit-forming pattern and a firstinsulation layer on a first carrier, the first circuit-forming patterninserted into the first insulation layer; forming inner circuit patternsand inner insulation layers over the first insulation layer, and forminginner vias connecting the inner circuit patterns positioned on differentinsulation layers; forming a second circuit-forming pattern on a secondcarrier and inserting the second circuit-forming pattern into a secondinsulation layer on an outermost side; removing the first carrier andthe second carrier; forming circuit-forming grooves by removing thefirst circuit-forming pattern and the second circuit-forming pattern,and forming via-forming indentations connected with the circuit-forminggrooves; and forming outer circuit patterns and outer vias by fillingthe circuit-forming grooves and the via-forming indentations with aconductive material.
 2. The method of claim 1, wherein at least one ofthe first circuit-forming pattern and the second circuit-forming patternis formed from a dissolvable material.
 3. The method of claim 2, whereinat least one of the first circuit-forming pattern and the secondcircuit-forming pattern is formed from a water-soluble resin.
 4. Themethod of claim 1, wherein at least one of the first circuit-formingpattern and the second circuit-forming pattern is formed from adetachable photosensitive resist.
 5. The method of claim 1, wherein atleast one of the first carrier and the second carrier is removed bydetaching.
 6. The method of claim 5, wherein at least one of the firstcarrier and the second carrier is any one of a tape, a film, and asheet.
 7. The method of claim 1, wherein at least one of the firstcarrier and the second carrier is removed by etching.
 8. The method ofclaim 7, wherein at least one of the first carrier and the secondcarrier is formed from a metal foil.
 9. The method of claim 1, whereinthe conductive material filled in the circuit-forming grooves and thevia-forming indentations is filled in by plating.
 10. The method ofclaim 9, further comprising: removing a portion of the conductivematerial by a leveling process, after filling the conductive materialin.
 11. The method of claim 10, further comprising, after the levelingprocess: forming a solder resist on at least one of the first insulationlayer and the second insulation layer and forming openings revealing theouter circuit patterns.
 12. The method of claim 1, wherein the innercircuit patterns are formed by a set of operations comprising: pressinginner-circuit-forming patterns formed on the inner insulation layers,such that the inner-circuit-forming patterns are inserted into the innerinsulation layers, and then removing the inner-circuit-forming patterns;and filling a conductive material in circuit-forming grooves formed byremoving the inner-circuit-forming patterns.
 13. The method of claim 12,wherein the inner vias are formed by processing via-forming indentationsconnected with the inner circuit patterns in the circuit-forminggrooves, and then filling a conductive material in the via-formingindentations.
 14. The method of claim 1, wherein forming the firstcircuit-forming pattern on the first carrier comprises: detachablysecuring a pair of the first carriers to each other and forming thefirst circuit-forming pattern on each of the first carriers.
 15. Amethod of fabricating a multilayer printed circuit board, the methodcomprising: forming a first circuit-forming pattern and a firstinsulation layer on a carrier, the first circuit-forming patterninserted into the first insulation layer; forming inner circuit patternsand inner insulation layers over the first insulation layer, and forminginner vias connecting the inner circuit patterns positioned on differentinsulation layers; forming a second circuit-forming pattern on a secondinsulation layer on an outermost side, and inserting the secondcircuit-forming pattern into the second insulation layer; removing thecarrier; forming circuit-forming grooves and via-forming indentationsconnected with the circuit-forming grooves, by removing the firstcircuit-forming pattern and the second circuit-forming pattern; andforming outer circuit patterns and outer vias by filling thecircuit-forming grooves and the via-forming indentations with aconductive material.
 16. The method of claim 15, wherein at least one ofthe first circuit-forming pattern and the second circuit-forming patternis formed from a dissolvable material.
 17. The method of claim 16,wherein at least one of the first circuit-forming pattern and the secondcircuit-forming pattern is formed from a water-soluble resin.
 18. Themethod of claim 15, wherein at least one of the first circuit-formingpattern and the second circuit-forming pattern is formed from adetachable photosensitive resist.
 19. The method of claim 15, whereinthe carrier is removed by detaching.
 20. The method of claim 19, whereinthe carrier is any one of a tape, a film, and a sheet.
 21. The method ofclaim 15, wherein the carrier is removed by etching.
 22. The method ofclaim 21, wherein the carrier is formed from a metal foil.
 23. Themethod of claim 15, wherein the conductive material filled in thecircuit-forming grooves and the via-forming indentations is filled in byplating.
 24. The method of claim 23, further comprising: removing aportion of the conductive material by a leveling process, after fillingthe conductive material in.
 25. The method of claim 24, furthercomprising, after the leveling process: forming a solder resist on atleast one of the first insulation layer and the second insulation layerand forming openings revealing the outer circuit patterns.
 26. Themethod of claim 15, wherein the inner circuit patterns are formed by aset of operations comprising: pressing inner-circuit-forming patternsformed on the inner insulation layers, such that theinner-circuit-forming patterns are inserted into the inner insulationlayers, and then removing the inner-circuit-forming patterns; andfilling a conductive material in circuit-forming grooves formed byremoving the inner-circuit-forming patterns.
 27. The method of claim 26,wherein the inner vias are formed by processing via-forming indentationsconnected with the inner circuit patterns in the circuit-forminggrooves, and then filling a conductive material in the via-formingindentations.
 28. The method of claim 15, wherein forming the firstcircuit-forming pattern on the carrier comprises: detachably securing apair of the carriers to each other and forming the first circuit-formingpattern on each of the carriers.
 29. A method of fabricating amultilayer printed circuit board, the method comprising: forming a firstcircuit-forming pattern and a via-forming pattern on a first carrier,and forming a first insulation layer; repeatedly forming inner circuitpatterns and inner insulation layers over the first insulation layer byprocesses of forming circuit-forming patterns and imprinting, andforming inner vias connecting the inner circuit patterns positioned ondifferent insulation layers; forming a second circuit-forming pattern ona second carrier and inserting the first circuit-forming pattern and thesecond circuit-forming pattern respectively into the first insulationlayer and a second insulation layer on an outermost side; removing thefirst carrier and the second carrier; forming circuit-forming grooves byremoving the first circuit-forming pattern and the secondcircuit-forming pattern, and forming via-forming indentations connectedwith the circuit-forming grooves; and forming outer circuit patterns andouter vias by filling the circuit-forming grooves and the via-formingindentations with a conductive material.